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MCP Tax Calculator in Claude Code

2026 US federal brackets, computed in the conversation. us_federal_tax applies the 2026 US federal brackets for a single filer — marginal rates by band with the standard deduction applied first — and returns tax owed plus the effective rate; it is a planning estimate computed exactly, not a filing tool, and the bracket table it uses is in the source where you can read it.

Pure compute over a bracket table you can read in the source, so --scope user and done; ask what-if questions in series and the answers are consistent because the table never changes mid-chat.

What you get in Claude Code

You say	Tool
Federal tax on 95,000 gross, single filer, 2026 brackets.	`us_federal_tax`
What if I gross 160,000?	`us_federal_tax`
Compare effective rates at 60k and 120k.	`us_federal_tax, twice`

The contract suite walks real stdio cases through the bracket table: 95,000 gross less the 15,750 standard deduction is taxed band by band with the marginal rate applied only above each threshold, the returned effective rate equals tax divided by gross, and a below-deduction income returns zero.

Install it in Claude Code

The file is .mcp.json, and the key inside it is mcpServers.

Scope	Path
local (default)	`~/.claude.json, this project only`
project	`.mcp.json at the repository root`
user	`~/.claude.json, every project`

If you also run Claude Desktop, the shortest path there is one click: tax-calc.mcpb from the latest release opens as an extension, with no JSON and no terminal. Claude Code reads its own config, so here it is:

From the terminal, against a built file:

claude mcp add --scope user tax-calc -- node /absolute/path/to/mcp-servers/servers/tax-calc/dist/index.js
claude mcp list    # health-check it before the first prompt

# or --scope project, committed to .mcp.json for the team

The node command above wants a built file. From a clone, once:

git clone https://github.com/theluckystrike/mcp-servers.git
cd mcp-servers && npm install
npm run build -w packages/mcp-license -w servers/tax-calc

That writes servers/tax-calc/dist/index.js, and its absolute path is the one argument the config needs.

The npm packages are not published yet, so the form below returns a 404 today. It is here because it is what the entry becomes the day the publish lands, with nothing else changed:

claude mcp add tax-calc -- npx -y @theluckystrike/mcp-tax-calc

No restart. The entry is picked up in the next session, and `/mcp` reconnects one on demand.

Nothing is published to npm yet, so the working install paths are the ones above: the .mcpb bundle from the latest release, a clone and build, or the hosted URL.

No install: the hosted endpoint

There is no hosted endpoint for this one yet. MCP Tax Calculator runs locally over stdio with the config above, which is also the only form in which it reads and writes files on your own disk. Thirty of the servers in this collection are served at https://mcp.zovo.one/mcp/<name> over MCP streamable HTTP; https://mcp.zovo.one/mcp/connect lists them and prints a ready URL for each.

Claude Code notes worth knowing first

The `--` is load-bearing: it separates Claude Code's own options, such as --transport, --env and --scope, from the command that runs the server. And the default scope is local, private to you and to the directory you ran it in, so adding it in the wrong folder leaves the tools absent with no error at all.

Free: Everything: one tool, no metering, no key. Pro is $19 once, verified offline.

Questions

Which scope should I use for MCP Tax Calculator?

Local, the default, writes ~/.claude.json and is private to you and that directory. --scope project writes .mcp.json at the repository root, shared through version control. --scope user loads it everywhere.

Why did my first prompt ignore the server?

Measured, not documented: of three fresh projects, one first prompt made zero tool calls although initialize answered in 1.05 seconds. Run claude mcp list once first: it prints Connected, and the next run used the tool.

Can I use MCP Tax Calculator without installing anything?

Not this one. The office suite starts every sibling server as its own child process, so it runs locally over stdio. Thirty of those children are hosted individually at https://mcp.zovo.one/mcp/<name> if you want a no-install route; open https://mcp.zovo.one/mcp/connect and it prints a ready URL for each.

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